An example of conventional magnetoresistance effect type thin film head is constructed in a manner as shown in FIG. 4 that an MR element 21 is disposed such that its longitudinal side is in parallel with a head (sliding) surface a, and electrodes 22a and 22b are led out from both ends of the MR element 21. In this case the two electrodes 22a and 22b are exposed to the head surface a. Thus, in the conventional thin film head, both electrodes 22a and 22b contact at the same time with a major surface of an electrically conductive recording medium, particularly, a major surface b (hereinafter merely referred to as a disc surface) of a magnetic recording medium 23 of a disc-like configuration which is formed by the sputtering process and used in a hard disc apparatus. When both electrodes 22a and 22b contact with the disc surface b, a resistance value changes not only in the MR element 21 but also in a portion between the electrodes 22a and 22b, thereby causing large noises.
In order to obviate the drawback, there has been proposed another example of a thin film head which is constructed in a manner as shown in FIG. 5 that an MR element 21 is disposed such that its longitudinal side is perpendicular to the head surface a, and among two electrodes 22a and 22b led out from the MR element 21, the one electrode 22a is exposed to the head surface a but the other electrode 22b is not exposed to the head surface a. In this case, the MR element 21 of the above-described example is thin in thickness, but as shown in FIG. 6, the electrodes 22a and 22b of this example are thick in thickness and are made of metal material of a high conductivity, so that even when the one electrode 22a contacts with the disc surface b, the change in electrical resistance value between the electrodes 22a and 22b is a negligibly small value, thereby not causing large noises. Further, since the MR element 21 of this example is constituted such that two magnetic material layers 21a and 21b sandwich an intermediate layer 24 of non-magnetic material therebetween, noises due to the Barkhausen effect, that is, the noises due to the movement of the magnetic domain walls can be prevented surely.
In general, when the hard disc apparatus is actually driven, the disc surface b repeatedly contacts with and separates from the head surface a, and the head surface a is spaced slightly from the disc surface b particularly when the disc is rotated.
In the thin film head of the example shown in FIG. 5, since the MR element 21 is supplied with a constant current, a voltage difference is generated between the disc surface b and the head surface a, particularly, the one electrode 22a of the head. In the state that the voltage difference is generated between the disc surface b and the one electrode 22a, when the head surface a closely approaches to the disc surface b or the head surface a contacts with the disc surface b, a large current immediately flows into the electrode 22a to cause electric discharge between the head surface a and the disc surface b, whereby the MR element 21 or the one electrode 22a is electrically broken by the discharge to thereby break the function of the head disadvantageously.
The present invention is performed in view of the above-described drawbacks of the conventional thin film head, and an object thereof is to provide a magnetoresistance effect type thin film head which is capable of reducing the change in voltage difference between the electrode of the MR element and the disc surface and preventing the breakages of the MR element and the electrode.